Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile

Abstract

Effects of avian gut-passage on seed germination are important to assess the effectiveness of frugivores in woodland regeneration, particularly in biodiversity hotspots that have a high incidence of avian frugivory. We examined the effect of avian gut-passage on seed germination in contrast to seeds that remain uneaten in five shrub species in Mediterranean central Chile and sought to determine the physiological mechanism(s) by which seed germinability is modified. Germination assays were conducted in a glasshouse for five common shrub species of the sub-Andean matorral: Azara dentata (Flacourtiaceae), Schinus polygamus and Schinus molle (Anacardiaceae), Cestrum parqui (Solanaceae), and Maytenus boaria (Celastraceae). We estimated germinability (final percent germination), dormancy length (time from sowing to first germination), mean length of dormancy of all germinated seeds, and contrasted germination rates of defecated versus manually extracted and pulp-enclosed seeds. Avian gutpassage increased seed germinability in four of the five shrub species studied-primarily through deinhibition via pulp removal. Minimum dormancy length was not modified by avian gut-passage for A. dentata, but was significantly shorter for S. molle and C. parqui. Mean dormancy length was significantly shorter in gut-passed seeds of A. dentata, S. molle and M. boaria. Avian gutpassage greatly enhanced the seed germination rates of three species, A. dentata, S. molle and C. parqui. We conclude that the positive effects of birds on seed germination facilitate the regeneration of sub-Andean shrublands, and that bird declines due to landscape change may impair recovery rates of successional or restored areas due to dispersal limitation.

NEOTROPICAL TREE PRODUCTION: INSIGHTS INTO GERMINATION, GROWTH AND OUTPLANTING FOR Maytenus boaria

“…A similar trend was observed in our study when comparing seeds from bird droppings and manually depulped seeds. However, contrary to results of Reid and Armesto (2011a) these treatments showed lower germination values than intact fruits. Gut digestion of M. boaria seeds by avian frugivores in the high mountain forests of central Argentina (mainly by Turdus chiguanco Lafresnaye and d'Orbigny) may not be as successful in stimulating seed germination as digestion by Chilean dispersers (Colorhamphus parvirostris Gould and Gray) and Xolmis pyrope Kittlitz) (REID; ARMESTO, 2011b).…”

“…Probably, the typical dry winters with irregular rains are adequate for a successful germination of M. boaria seeds. Nevertheless, further research in germination success of the species in central Argentina is needed, since the best performing treatment reached only 29.2 % germination, which is still low compared to germination values of up to 87.5 % reported for central Chile by Reid and Armesto (2011a).…”

“…Maytenus boaria is commercially produced for reforestation purposes in the central and southern Andes of Chile and Argentina, where most research on this species has been conducted; however, there are no reports indicating difficulties or failures in plant production and planting establishment (e.g. DONOSO, 2006;ARMESTO, 2011a;ARMESTO 2011b). Conversely, forest restoration projects within the M. boaria range in the high mountains of central Argentina have faced several production difficulties due to the low germination rates of this species.…”

Leaf litter is essential for seed survival of the endemic endangered tree <i>Pouteria splendens</i> (Sapotaceae) from central Chile

“…This is because animal seed dispersers carry the seeds away from parent plants, decreasing the probability of seed mortality associated with host-specific parasites and predators (i.e., escape hypothesis) (Janzen, 1970). Also, in the case of fleshy fruits being dispersed, vertebrates can improve regeneration by removing the pulp from the seeds through their guts, increasing the capacity for seed germination (Traveset, 1998;Wenny, 2001;Reid and Armesto, 2011).…”

Frugivory of Persea lingue (Lauraceae) and its effect on seed germination in southern Chile

“…Many of these studies described vertebrates (reptiles, birds and mammals) as dispersers of plant seeds. Other interactions, like secondary dispersal and predation, have scarcely been included in ecological seed studies in southern Chile, and few studies have included the effect of seed consumption by vertebrates in seed germination , Soto-Gamboa & Bozinovic 2002, Traveset et al 2006, Reid & Armesto 2011.…”